A specially formatted sequence of characters representing a location on the Internet. The URL contains three parts: the network protocol, the host name or address, and the file location. The network protocol determines the underlying Internet protocol to be used to reach the location; it consists of a standardized name of a protocol followed by a colon and two forward slashes (://). Common protocols in URLs include ftp://, http://, and mailto://. The host immediately comes after the protocol definition, represented by its fully qualified hostname, as found in the DNS or by its IP address. For example, a URL of http://www.askme.com contains both the protocol and the host data required to access this Website. The file part of a URL defines the location of a resource on the server. Resources are files that can be documents, graphics, or plain-text files. A URL such as http://www.askme.com has an implicit file location that most Web servers (for example, Apache) interpret to refer to a specific filename such as “index.htm.” All other files exist in a hierarchical directory structure under the root, such as /library/glossary/abglossary .htm. A full URL would look like this: http://www.askme.com/library/glossary/abglossary.htm. When creating HTML pages, developers can choose to use relative file locations—such as “../pics/image.gif,” which locates the file “image.gif” in a subdirectory “pics’ of the directory containing the current file—or complete URLs, but most on the Internet use complete URLs. Further Reading. About, Inc. URL. [Online, 2004.] About, Inc. Website. http:// compnetworking.about.com/library/glossary/bldef-url.htm.
A universal address for resources on the internet, which is most commonly used for websites.